1. Field of the Invention
The invention relates to a display, and more particularly, to a shift register for releasing an image retention and a method for releasing the image retention.
2. Description of Related Art
In the widely used technique of the thin film transistor (TFT) liquid crystal display (LCD) is to apply the shift register made of amorphous silicon on the gate driver and the source driver of the display panel. The thin film transistor technique has the advantages of low cost of integrated circuit, simple manufacturing process in module stage, and high glass substrate usage. While the liquid crystal display displays images, the storage capacitors in the thin film transistors are used to maintain to pixel voltage. Therefore, when the pixel voltage is not discharged during the power off period, the image retention happens. Conventionally, before the display panel is turned off, the gate drivers pulls up the voltages of the gate lines of the display panel from the negative voltage to a high voltage level so as to simultaneously turn on the thin film transistors of all pixels. Therefore, the voltage of each of the pixels can be effectively discharged before the display panel is turned off so that the problem of the image retention can be avoided. However, by using the shift register made of amorphous silicon, the structure of the conventional shift register cannot support the step for pulling up the voltages of the gate lines from the lower voltage level to the higher voltage level during the power-off period. Therefore, the problem of the image retention happens and is one of the major problems of the amorphous silicon shift register.